Practical 7 Building a Pipelined Processor
Objectives
This section is not a list of tasks for you to do. It is a list of skills you will have or things you will know after you complete the practical.
Following completion of this practical you should be able to:
- Construct a verilog implementation of a very basic pipelined processor that supports R and I-type RISC-V instructions.
- Trace code as it executes through a simulated pipelined processor
- Use waveform diagrams to debug a processor implementation
- Use verilog test benches and a testing framework to test a processor implementation
Guidelines
-
Because you will be iteratively adding functionality to one processor module, we strongly recommend that you periodically add and commit your progress to git as a backup.
-
This is a reasonable quick-reference for verilog: Compact Summary
Your Tasks
Follow this sequence of instructions to complete the practical.
This practical will all be done in your D-group
repository
0 Obtain your C-group
git repo
1 Implement R-type datapath (no control yet)
-
Trace on the provided DP diagram
-
Design your pipeline stage registers' contents
- build each, call them
IF_ID_Reg
, etc. so the instances can beIF_ID
or similar. - For each "thing" in the register, make the output named that thing, and an input should have the same name with an
_in
suffix. For example:input wire [31:0] inst_in, output reg [31:0] inst,
- Be sure to include the clock as an input.
- In the body of the module, create an always block to copy the inputs to their corresponding outputs.
- build each, call them
-
Create
Processor.v
that has instances of all your pipeline stage registers -
Between the registers, instantiate the components you need
- Register File
- PC
- ALU
- No data memory yet (use DP_Memory.v from practical, but only connect the "A" ports.)
-
Connect the components to your pipeline stage registers
-
The Memory cycle will just pass data through from
EX_MEM
toMEM_WB
. -
Your
WB
cycle will refer to the register file in yourID
cycle.
2 Add control to your datapath
- Use your single cycle control!
- Put it into
ID
- Write the EX/Mem/WB outputs into your
ID_EX
pipeline stage register - Update all your stage registers to have control blocks.
3 First Test in modelsim
TODO: CREATE BASIC R-TYPE MODELSIM TEST FOR THEM
- Edit our basic R-type test to use your processor (see comments in test).
- New modelsim project
- Add all the .v files
- compile
- run the basic test
- Build a waveform to show all your stages.
- add a divider between each stage
- HINT:
do opcodes.do
in the console will add some new "Radix" values that will display opcodes and functs as useful words. - Save your waveform.
- Run the tests
- Fix any errors.
4 Add support for the remaining R-types
- Do it
- Test R-types using
tb_Pipe.v
- Edit the
pipeline_test_tools.vh
file - Tour of test bench file?
- Edit the
5 Add I-types (no data memory yet)
- Trace on dp diagram
- Add any new traced wires to verilog datapath
- Add control (or connect it)
- You'll need an ALUSrc mux
- Write tests (here's some assembly. Assemble this with your assembler, then add new task to
tb_Pipe.v
to use it. - Run tests
- On worksheet, explain why this set of instructions is sufficient to test I-types, or how you changed it to be better.
6 If you have time...
Work ahead (go start Practical 8)
Turn It In
Grading Rubric
General Requirements for all Practicals:
- fits the need
- discuss performance
- tests for correctness
- iteration and documentation
Fill out the Practical Worksheet
In the worksheet, explain how you satisfy each of these items. Some guidelines:
- None of these answers should be more than 100 words.
- For item 1, ??
- For item 2, explain how the pipelined implementation will be faster than your single-cycle ??
- For item 3, describe how you designed the tests for I-type and how you know it's enough
- For item 4, ?? documentation of your new test? documents in comments?
Practical 7 Rubric items | Possible Points |
---|---|
Practical Worksheet | 25 |
R-Type and tests | 30 |
I-Type and tests | 30 |
Custom Tests | 10 |
Extra points | 5 |
Total out of | 100 |
For extra points, you could:
- oh man, I dunno
-
Submit your completed Practical Worksheet to gradescope.
-
Practical code will be submitted to your
D
git repository as new files and committed modifications to the repo we provided you. You must include your name and your teammates' names in a comment at the top of all files you submit.